Susceptibility of Sitophilus zeamais (Mostch.) (Coleoptera: Curculionidae) to Beauveria bassiana and Metarhizium anisopliae

Abstract

Evaluation of eleven Metarhizium anisopliae and six Beauveria bassiana isolates against the maize weevil Sitophilus zeamais was conducted under laboratory with the objectives of identifying the most virulent locally available fungal isolates, and determining the dose mortality response. The pathogenicity (virulence) of the entomopathogenic fungi was determined using LT 50 and percent mortality at the conidial concentration of 1 x 10 8 ml-1. The most virulent isolates of M. anisopliae (PPRC-2, PPRC-14 and PPRC-51) and B. bassiana (PPRC-GG and PPRC-HH) caused 84.4% to 98.3% mortality to S. zeamais. These isolates had LT 50 ranging from 3.8 to 4.3 days. The dose response study with the isolates PPRC-2, PPRC-14 and PPRC-51 at doses ranging from 1x 10 4 to 1x 10 8 conidia ml-1 revealed susceptibility of the S. zeamais with mortality ranging from 25 to 95.5%. There was an increase in the resulting LT 50 from 4.0 to 11.9 days with a decrease in conidial concentration from 1x 10 8 to 1x 10 4 conidia ml-1. PPRC-2 showed the lowest LC 50 (1.46x 10 conidia ml-1) followed by PPRC-14 and PPRC-51 (3.5x 10 5 and 3.9x 10 5 conidia ml-1 , respectively). In conclusion, the isolates PPRC-2, PPRC-14, PPRC-51, PPRC-GG and PPRC-HH, can be considered as a potential candidates in the development of mycoinsectisdes against S. zeamais.

Influence of Some Biological Control Measures on Tribolium castaneum (Coleoptera: Tenebrionidae)

“…As well as M. anisoplia had greater bioinsecticidal efficacy against both the third larval instar and the adult of T. castaneum than B. bassiana. Similar results reported that, when B. bassiana or M. anisopliae were applied to S. zeamais, the latter resulted in increased mortality and a lower median survival time (Teshome and Tefera, 2009). M. anisopliae was extremely efficient against T. confusum larvae because its larvae eat and develop in the exterior region of the seed, increasing the probability of picking up conidia (Kavallieratos et al, 2006).…”

“…M. anisopliae was extremely efficient against T. confusum larvae because its larvae eat and develop in the exterior region of the seed, increasing the probability of picking up conidia (Kavallieratos et al, 2006). Teshome and Tefera (2009) found that increased the fungal concentration of both M. anisopliae and B. bassiana isolates against S. zeamais increased the amount of conidia attached to the insect. The weak progression of infection at lower doses of B. bassiana caused lower mortality of Plutella xylostella (Yoon et al, 1999).…”